Yield regulation method for eucalypt plantation forest based on optimization of growing stock and soil erosion

Abstract

The grouping of site quality and controlling of soil erosion in eucalypt plantation forest is very important to be considered in the yield regulation method establishment. The objective of this research is to establish the yield regulation method that can provide the same yield every year with soil erosion constraint that does not exceed determined threshold. To achieve this objective the following stages are required: preparation of site quality class, determination of erosion hazard level and determination of residual stand density so that soil erosion can be tolerated. Data were collected from permanent sample plots and observations in the field. Stand characteristics, soil runoff and erosion were analyzed using regression, clustering site quality and soil erosion hazard level. The research results showed that yield regulation method based on optimization between growing stock and soil erosion control may giving both the optimal sustainable annual wood production and soil erosion control, so that land productivity can be maintained continuously. With this yield regulation method, the site quality is getting better, cutting cycle is getting shorter. Group of site index (Bonita) I and II has a maximum volume increment at the age of 8 years, while the bonita III and IV have a maximum volume increment at the age of 7 years. Soil erosion will increase with the increase of sloping terrain. While increasing stand age will decrease soil erosion. The maximum limit of tolerable soil erosion was at the slope of 33%. Slopes of 34-45%, 46-58%, and more than 58% , require crown cover of 21%, 38%, and 53% respectively which are equivalent to residual stand density of 288 trees/ha, 530 trees/ha, and 735 trees/ha respectively. The study found that the optimum cutting cycle in the eucalypt plantation forest is 7 years. The yield regulation method based on modified Von Mantel formula is AY’ is annual yield based on modified Von Mantel formula, AY is annual yield based on Von Mantel formula, AG is actual growing stock, R is cutting cycle, and FkD is Darwo correction Factor for soil erosion constraint.